a) Field of the Invention
The invention is directed to a valve device for connecting to a cryopump. The invention is further directed to a pump arrangement comprising a cryopump with a backing pump connection flange to which a valve device is connected.
The valve device comprises a purge gas line in which a purge valve is arranged and which serves to supply a purge gas to the cryopump during a regeneration process of the cryopump.
b) Description of the Related Art
Cryopumps are known. They have cooled adsorption surfaces for adsorbing gases. A regeneration in which the adsorption surface is heated is occasionally required. Adsorbed gas containing hydrogen, for example, is released during regeneration. In order to prevent any risk owing to released gas, for example, to prevent the risk of explosion, a purge gas which dilutes the released gas is supplied during regeneration of the cryopump. The purge gas is an inert gas, usually nitrogen. A supply line arranged inside the cryopump serves to supply the purge gas to the adsorption surfaces. In known cryopumps, a connection flange is arranged at the housing of the cryopump. A purge gas line through which the purge gas is supplied can be connected to the supply line by means of the connection flange. A purge gas valve which can be opened and closed is arranged in the purge gas line.
The gas released during the regeneration process, together with the supplied purge gas, leads to an overpressure which is relieved through a pressure relief valve. This pressure relief valve is usually arranged at an intermediate piece which is connected to a backing pump connection flange of the cryopump on one side and to a backing pump valve on the other side. The backing pump valve leads to a backing pump by means of which the cryopump and a vacuum chamber to which the cryopump is connected can be pumped down to a pre-vacuum or roughing pressure. The backing pump valve is usually constructed as an angle valve or corner valve.
As a further safety precaution, a diluting gas which is an inert gas, usually nitrogen, is mixed in with the gas flowing out of the pressure relief valve during a regeneration process of the cryopump.
Servicing or exchange of the cryopump in a conventional pump arrangement of the kind described above is relatively complicated because of the parts to be disassembled.